1. Field of the Invention
The present invention relates to a mixer, a mixing device, and a medical component-measuring unit. More particularly, the present invention relates to a mixer capable of mixing quickly several liquids including at least one liquid that is prone to easily gel or solidify, which mixer has a structure preventing the liquid from gelling. The invention also relates to a mixing device, with the mixer incorporated, capable of mixing the several liquids so as not to cause the liquid to gel or solidify. The present invention further relates to a medical component-measuring unit including the mixer or the mixing device.
2. Description of the Related Art
When several liquids including at least one liquid that is prone to gel or solidify are mixed, the mixing operation must be done quickly and adopt a measure to prevent the liquid from gelling or solidifying. In, for example, an artificial endocrine pancreas device, the concentration of the glucose component in blood is measured by measuring a mixed liquid of a blood sample taken from a patient and a reagent. In order to accurately measure the glucose concentration, it is necessary to mix the blood sample and the reagent uniformly and a measurement has to be done in such a quick manner that the measurement is completed before the blood sample coagulates in the fluid channels. Please note that the word “coagulate” includes the meanings of “gel” and “solidify”.
As a technique of mixing several liquids flowing in micro-scale channels are proposed “microchannels for helical flow” (Non-patent Document 1). The following is a passage from non-patent document 1: “There is a micro-mixer which causes a helical flow in a microchannel by oblique grooves inscribed in the bottom of the channel, which increases contact interfaces of samples and expedites diffusion and mixing. (A. D. Stroock, et al., Chaotic Mixer for Microchannels, Science, Vol. 295, pp. 647-651, 2002) We thought that smaller pitches of the helix of a helical flow would improve the efficiency of mixing and proposed a “microchannel for high-efficiency helical flow” in which oblique grooves are formed in the three walls of the channel, as shown in FIG. 7 (b).” The proposed “microchannel for high-efficiency helical flow” is considered to be a very excellent device when it is applied to a micro-scale channel that has a relatively long channel compared to the area of the transverse section of the channel. However, some more improvement is necessary for applications, such as artificial endocrine pancreas devices, which should have a channel as short as possible to reduce a time period for which the mixed liquid flows through the channel, or the time constant.
We conducted a search was conducted on B01F5/00@D as FI code with patent documents that were published on and after Jun. 1, 1989. Some of the documents are listed below.    Patent Document 1: JP 2006-015292 A    Patent Document 2: JP 2006-015272 A    Patent Document 3: JP 2006-007063 A    Patent Document 4: JP 2005-342944 A    Patent Document 5: JP 2005-324080 A    Patent Document 6: JP 2005-319419 A    Patent Document 7: JP 2005-314424 A    Patent Document 8: JP 2005-313042 A    Patent Document 9: JP 2005-305219 A    Patent Document 10: JP 2005-288254 A    Patent Document 11: JP 2005-279542 A    Patent Document 12: JP 2005-246184 A    Patent Document 13: JP 2005-238232 A    Patent Document 14: JP 2005-230586 A    Patent Document 15: JP 2005-224799 A    Non-patent Document 1: http://www.shoji.comm.waseda.ac.jp/˜mf/,fjp/rasen.htm
When several liquids, each in a very small amount, which have a small flow velocity and forms laminar flow, are mixed, interlayer mixing or mixing between the layers does not progress. Besides, it is difficult to place a rotatable mixer in a channel with a small diameter to mix several kinds of liquids each in small amounts while they are being transferred. Even if such a mixer is placed in the channel, it makes the structure of the device complicated. When a blood sample and a reagent are mixed with a mixing device or by other structures, the device and structures become obstacles against the fluid flow, and the liquids are caught by the obstacles and remain on places thereof, which leads to the formation of thrombi. Also, coiled tubes, made by winding a tube like a coil, are employed as a device mixing a blood sample with a reagent in applications such as artificial endocrine pancreas devices. The coiled tube is so designed that the mixing of a blood sample and a reagent is achieved while the blood sample and the reagent are passing through the coiled tube gradually. Although this kind of coiled tubes somehow achieves the mixing of a blood sample and a reagent, the length of the coiled tube reaches as much as 320 mm. Artificial endocrine pancreas devices, employing such a long coiled tube as mixing device, have a large time constant, which is problematic with this kind of devices.